1. Field of the Invention
This invention pertains to resilient seal rings employed in tubular connections and the connections employing such seal rings.
2. Description of the Prior Art
High performance or premium tubular connections are normally designed not to leak and to retain both fluid and gas even under harsh operating conditions. Although the general configurations of the threads employed in such connections and the metallic conical surfaces adjacent the actual threads are often designed to provide suitable metal-to-metal seals that seal and do not leak, many thread connections also employ resilient seal rings in addition. In fact, in some cases, total seal reliance is placed in such a ring, not just secondary or tertiary sealing reliance.
However, the more normal condition encountered in practice is for the connection to have a metal-to-metal conical seal occurring at a given location, e.g., on the forward end of the pin member, with the resilient seal ring being included in a groove therein. In such a location, the ring contacts the opposing or mating sealing surface of the box member. The box member can be the adjacent tubular section with the box threads incorporated into the end thereof or the box member can be a coupling have box threads. In either case, the sealing action between the pin member and the box member is similar.
In addition to or instead of having a sealing surface at one or more conical surfaces adjacent the thread set or sets, as mentioned above, a connection can also seal in its threads. However, it is still often desirable to use a resilient seal ring even in such a connection. For example, a resilient seal ring can be included in the Series 500 Type 563 connection of the Hydril Company, which connection features a single step tapered dovetail wedge thread design having a shallow taper, mis-matched angle, conical metal-to-metal seal. Although such a connection seals both in threads and on its adjacent conical surfaces, sealing is further enhanced with the inclusion of a sealing ring in a suitable groove included in the conical sealing surface forward of the thread set on the pin member.
The conventional seal ring employed in such a location is rectangular in cross-section and snugly fits into the groove made therefor. However, it is to be noted that the operating conditions for such a ring are often extremely harsh. The temperatures may be up to around 300.degree. F. The pressures may be up to around 20,000 psi. There may be thermal cycling between a very hot condition and a relatively cooler one. There may be many break outs and make ups of the connection.
It has been observed that in testing of a resilient seal ring at the place noted, the rectangular cross-section seal ring normally employed in similar situations have sometimes resulted in leakage under such test conditions.
Therefore, it is a feature of the present invention to provide an improved resilient seal ring for sealing purposes in a tubular connection.
It is another feature of the present invention to provide an improved connection wherein a resilient sealing ring is an important part, the improvement including a more reliable seal at the ring than attained in the prior art.